The Las Vegas callbacks were held at Planet Hollywood Resort and Casino in Las Vegas, Nevada.[6] 172 dancers were invited to participate in the callback auditions. This number was cut to 32 dancers, 16 male and 16 female, before the announcement of the season's top 20 contestants. Las Vegas week included the following rounds, with cuts made after each:

Contestants are listed in reverse chronological order of elimination. The song for the eliminated female contestants was "Already Gone" by Kelly Clarkson. The song for the eliminated male contestants was "On Your Own" by Green River Ordinance.

On May 21, 2009, SYTYCD aired two males performing ballroom dance together for the first time, with dancers Misha and Mitchel performing a Samba.[7] The dance couple's introduction on the show, and the judges' subsequent comments, have been criticized as homophobic. The two men were introduced with The Weather Girls' "It's Raining Men" played in the background. After the couple performed, judge Nigel Lythgoe said, "I think you'd probably alienate a lot of our audience. We've always had the guys dance together on the show but they've never really done it in each other's arms before. I'm really one of those people that like to see guys be guys and girls be girls on stage. I don't think I liked it, to be frank."[8] He later went on to say that he'd like each man to dance with women and that: "You never know, you might enjoy that, too." The segment closed, and the song "It's a Man's Man's Man's World" is played in the background, which contains the lyrics: "This is a man's world, but it wouldn't be nothing, nothing without a woman or a girl." Cat Deeley went on to say that the pair were "out."

Lythgoe issued a formal apology letter later that week, stating that he regretted "poor word choices" and that he realized how his comments could be "misconstrued." He went on to say that he "believe[s] the sexual orientation of an auditioner or contestant is irrelevant... the fact that I have unintentionally upset people is distressing to me... I have made mistakes that I must learn from."[9]

So You Think You Can Dance went on tour through 40 cities across the US and 1 city in Canada, Toronto.[10] Nigel had also announced that Phillip Chbeeb and Caitlin Kinney would also be going on the tour as swing dancers since they made it to the top 12 before being cut.